The present invention relates to a unit suitable for industrially producing high purity hydrochloric acid having an extremely low impurity concentration, and to methods for producing hydrochloric acid using the same.
Conventionally, high purity hydrochloric acids are industrially produced, as shown, for example, in FIG. 4, by generating hydrogen chloride gas using a burner hydrochloric acid method or a by-product hydrochloric acid method or the like in a hydrogen chloride gas generator 61, by feeding this to an absorbing reactor 63 through a gas supply pipe 62, and by allowing this to be absorbed in ultrapure water within this reactor 63. The gas supply pipe 62 mentioned above consists of, for example, vinyl chloride resin to nearly the upstream position of the absorbing reactor 63. Valve 65 controls the flow through pipe 64 to absorbing reactor 63. Such materials are not affected by water-free-hydrogen chloride, but are affected by water-containing hydrogen chloride, and elutes such impurities as iron, copper, zinc, nickel, sodium, calcium, potassium, etc. Therefore, materials of the inner wall of the absorbing reactor 63, the part inserted inside the reactor of the gas supply pipe and the product extraction pipe on the downstream of the absorbing reactor are made of acid resistant materials such as fluororesin and the like. By this, impurities can be controlled to elute to a certain extent, but such a composition was still not adequate to produce a high purity hydrochloric acid.
Now, in recent years, in the light of improving the yield of products using hydrochloric acid, there is a need for high purity hydrochloric acid having and impurity concentration smaller than 1 ppb with conventional methods, the impurity concentration of hydrochloric acid is at most 5 ppb or below, the removal of impurity to less than 1 ppb being difficult. Moreover, if hydrochloric acid with the impurity concentration smaller than 1 ppb is to be produced industrially, the products are available only when the quality is acceptable, resulting in increased inspection frequency of generated hydrochloric acid. These complex processes make it difficult to constantly produce a large amount of high purity hydrochloric acid.
Therefore, the purpose of the present invention is to provide a simply-constructed unit for producing hydrochloric acid and a method which allows the efficient production of a large quantity of high purity hydrochloric acid having an extremely low impurity concentration.